Topband:mode separation...small stndx oppty

[Chuck Hutton]

I don't think the DSL is likely to cause interference. The common
implementation (OFDM) and the less common implementation (CAP) both occupy
spectrum up to just above 1.1 MHz. 

As for "notches", only OFDM can do that, and it does it by looking at the
S/N for each subcarrier individually and if a subcarrier has a constant
problem that particular subcarrier is simply is not used. But that
capability is only used to avoid interference from MW broadcast stations due
to the spectrum used. BPL does indeed have notches (from some manufacturers)
for amateur bands - perhaps you were thinking of that?

There's always the possibility of interference from routers, switches, the
DSL modem and cabling past the DSL modem.


Chuck

-----Original Message-----
From: topband-bounces at contesting.com [mailto:topband-bounces at contesting.com]
On Behalf Of John Kaufmann
Sent: Friday, April 23, 2004 12:10 PM
To: Jim Brown; topband at contesting.com
Subject: Re: RE: Topband:mode separation...small stndx oppty


Jim Brown wrote:

> At a SMPTE meeting last week, I was talking about this with some hams
> who also work in broadband and in broadcasting. One of them suggested
> that DSL might be responsible for some trash on 160. Any thoughts on
> this?  I don't have DSL myself -- I use a cable modem, with its own
> (much higher frequency) set of problems. 


I have a DSL modem at home and I don't see any trace of interference on 160
(or any other band) from the modem.  I do sometimes cause the modem to lose
sync when I transmit but that's a different issue.

Supposedly the DSL signaling spectrum has notches defined specifically in
the amateur bands to avoid interference.  I have no idea if and how well
these are implemented in practice, but certainly my experience doesn't
indicate anything negative.

73, John W1FV

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